Autocomplete function in code editor

[tmhglnd]

Implementing an autocomplete that has a list of all the available functions and sample/synth names.

The playground still used CodeMirror5, so probably have to look at using: https://codemirror.net/5/addon/hint/show-hint.js (also see the manual https://codemirror.net/5/doc/manual.html). Or work on updating to newest CodeMirror and use https://codemirror.net/examples/autocompletion/